Elastomeric materials which are not thermoplastic cannot be welded to thermoplastics. They have to date therefore generally been bonded by adhesive bonding. This is complicated, and owing to the use of solvents, environmentally undesired. Furthermore, some thermoplastics are poorly accessible to adhesive bonding, for example polyethylene.
It is known (EP-B-0751865, DE-A-3621030, EP-A-159169, EP-A-483569, U.S. Pat. No. 5,279,693, FR-A-1506163, WO 89/10832) that two thermoplastic parts can be bonded by means of laser beams for which the upper of the two parts is transparent and which are absorbed in the region of the weld joint. As a result of the absorption in a thermoplastic material, the latter becomes molten and is therefore directly capable of effecting welding to the counter-surface. This is also true when one of the two parts consists of a thermoplastic elastomer (Hänsch et al., “Harte und weiche Kunststoffe mit Diodenlaser verbinden” [Bonding hard and soft plastics using diode lasers] in Kunststoffe [Plastics] 1988, pages 210-212. A precondition for a reliable cohesive bond is, however, that the polymers are miscible with one another, which is often problematic precisely when one of the two parts consists of an elastomer. Difficulties often also arise because the heat draws away toward the back in the part absorbing the radiation and is therefore not available for welding, so that weld faults occur.
The invention is concerned especially with the bonding of a thermoplastic polymer layer to the surface of an elastomer. It is the object of the invention to provide a reliable bonding method which manages without an adhesive.